Host-Specific Adaptation of <i>Legionella pneumophila</i> to Single and Multiple Hosts
Bibliographic record
Abstract
Legionella pneumophila is an endosymbiotic bacterial species able to infect and reproduce in various protist and human hosts. Upon entry into human lungs, they may infect lung macrophages, causing Legionnaires' disease (LD), an atypical pneumonia, using similar mechanisms as in their protozoan hosts, despite the 2 hosts being separated by a billion years of evolution. In this study, we used experimental evolution to identify genes conferring host specificity to L. pneumophila. To this end, we passaged L. pneumophila in 2 different hosts-Acanthamoeba castellanii and the human macrophage-like cells U937-separately and by switching between the hosts twice a week for a year. In total, we identified 1,518 mutations present in at least 5% of the population at the time of sampling. Forty-nine mutations were fixed in the 18 populations at the end of the experiment. Two interesting groups of mutations included (i) mutations in 4 different strain-specific genes involved in lipopolysaccharide (LPS) synthesis, found only in the lineages passaged with A. castellanii and (ii) mutations in the gene coding for LerC, a key regulator of protein effector expression, which was independently mutated in 6 lineages grown in presence of the macrophage cells. We propose that the mutations degrading the function of the regulator LerC improve the fitness of L. pneumophila in human-derived cells and that modifications in the LPS are beneficial for growth in A. castellanii. This study is a first step in further investigating determinants of host specificity in L. pneumophila.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".